1. Field of the Invention
The invention relates to a light guide device and particularly relates to a light guide device including a wedge-type light guide plate.
2. Description of Related Art
A backlight module usually includes a light guide plate that is used for guiding the scatter direction of the light generated by a light source, so as to increase the brightness and maintain the brightness uniformity of the panel, and further to transform the point light source or linear light source of the backlight module into a planar light source for the liquid crystal display panel. Therefore, the material property and the design and fabrication of the surface diffusion pattern of the light guide plate are all influential to the overall optical design and the brightness/uniformity control of the backlight module.
FIG. 1 is a schematic side view depicting a wedge-type light guide plate of a conventional light guide device. In order to satisfy the demand for high-brightness backlight module and miniaturized light guide plate, the conventional light guide plate is designed to be wedge-shaped. However, most of the current wedge-type light guide plates have lower light incidence efficiency and encounter the problem that light is emitted outwards soon after reaching the light guide plates, and as a result, light leakage easily occurs outside the effective light-emitting region 20, as shown in FIG. 1. In addition, as illustrated in FIG. 1, after the thickness H2 of the conventional wedge-type light guide plate is reduced, a difference between the height H1 of the incident plane and the thickness H2 of the effective light-emitting region increases the slope of wedge bevel 10. As a result, the light is more easily emitted soon after reaching the light guide plate and makes the light leakage problem worse at the wedge bevel 10. For the above reasons, how to change the wedge bevel structure to improve light coupling efficiency and reduce light leakage has become an important issue in this field.